This invention relates to an attachment assembly for the connection of large excavation teeth to the shovel or dipper bucket of large excavation equipment. More particularly, this invention relates to a novel protective wear cap for use in an attachment assembly which employs an adaptor and a securement pin for securing a large excavation tooth to the excavating equipment for the purpose of reducing the wear on the adaptor during use and thereby significantly decrease the costs associated with part replacement.
During the course of large ground excavation projects, it has been found that it is preferable to make the excavation teeth a separate and distinct part, readily attachable and detachable to the main excavation implement, rather than forming the excavation teeth integrally with the main implement. This allows for easy replacement of individual teeth should a tooth become broken or dulled through wear.
Traditionally, the excavation tooth has a hollow interior portion which fits onto a forwardly projecting nose piece on an adaptor secured to the shovel or dipper bucket of the excavation equipment. Pin means are thrust through an orifice in the excavation tooth and through a channel in the nose piece to retain the tooth in position on the nose piece. Because of the tremendous pressure which is exerted upon the tooth during excavation, it is desirable to displace the pin transversely to the excavation movement, which is normally and primarily in the vertical direction. Parallel placement of the pin allows the pin to wobble under the force generated by the excavation implement. This wobble causes early failure of the pin causing the tooth to drop off.
For many years, a simple arrangement involving a single horizontally displaced pin was sufficient. Subsequently, however, the excavation implements began utilizing closely spaced teeth, thereby making it difficult, and in some instances impossible, to displace the traditional horizontal pin within the excavation tooth. Therefore, there existed a need in the art for a locking assembly whereby the excavation tooth may be engaged and disengaged by working vertically.
Another problem historically encountered with devices of this type stems from the fact that the nose piece of the adaptor can become worn so that there is not a precise fit between the tooth and nose piece. This allows for some horizontal movement of the tooth on the nose piece as well as some vertical or rotational movement of the tooth with respect to the nose piece. A solution to these problems is found in U.S. Pat. No. 4,516,340 which discloses an attachment assembly including a nose piece projecting from an adaptor, an excavation tooth and a single vertically mounted securement pin, wherein the nose piece defines a tapered extension for carrying the excavation tooth. The tapered extension defines a recessed horizontal stabilizing surface at the extended end thereof which is bordered by a vertical stabilizing wall. The tooth has a channel therein corresponding to the configuration of the tapered extension of the nose piece so that the nose piece can fit snugly thereover in a mating relationship and the securement pin extends vertically through the tapered extension of the nose piece and the excavation tooth securing the tooth in place on the nose piece. The mating relationship of the channel walls in the excavation tooth with the recessed horizontal stabilizing surface and vertical stabilizing walls prevent lateral and vertical, or rotational movement of the tooth with respect to the nose piece to provide a secured and durable yet readily detachable excavation tooth assembly.
While such an attachment assembly provided improved securement of a large excavation tooth in a row of closely spaced teeth on large excavation equipment utilizing only a single vertical pin it has been found that, over a period of time, the adaptor became worn and must be replaced. The wear occurs because of the abrasion of the forward portion of the adaptor caused by the material passing thereon during use and by continual contact between the rearward end or base of the tooth and the portion of the adaptor rearwardly adjacent the nose piece and the great forces exerted on that portion of the adaptor by the tooth during use. While replacement of excavation teeth due to wear is a common and necessary occurrence, replacement of the adaptor is highly undesirable due to its significant size, weight and costs. It would therefore be very desirable to provide an attachment assembly which retains all of the advantages inherit in the attachment assembly disclosed in the aforesaid U.S. Pat. No. 4,516,340, but which reduces the wear on the adaptor, thereby substantially reducing the parts and labor costs associated with its replacement.
In an effort to retain the benefits of the aforesaid patented attachment assembly, protective wear caps were developed which were carried by the forward portion of the adaptor and positioned thereon so as both to shield the adaptor from the abrasion of the material passing thereover during use and to be abutted by a portion of the rearward end or base of the tooth and thus sustain the wear caused by frictional engagement with the tooth which was previously borne by the adaptor. When the wear cap became overly worn, it could then be replaced far more economically than the much larger and expensive adaptor. While such wear caps did prolong the life of the adaptor in many instances they tended to create additional durability problems which resulted from the manner in which they were configured and secured to the adaptor.
With the previously developed protective wear caps, the adaptor was provided with an integrally formed dove-tailed projection which extended axially and rearwardly from the nose piece and was axially received in a correspondingly configured channel in the underside of the wear cap. To manufacture such a configuration with the tolerances necessary to prevent binding of the mating adjacent surfaces in the attachment, it was necessary to machine the mating dove-tailed surfaces, which is quite expensive. In addition, the dove-tailed configuration defined acute angles in the mating parts which created stress risers on both the wear cap and adaptor which on occasion led to failure of either the wear cap or the adaptor.
Another problem with such protective wear caps was their tendency to slide down the nose piece during tooth replacement which made tooth replacement a more laborious and time consuming task. This resulted from the axial mounting of the wear cap on a tapered surface of the adaptor. The protective wear cap and mating adaptor configuration of the present invention enables the attachment assembly disclosed herein to retain the benefits of the attachment assembly disclosed in U.S. Pat. No. 4,516,340, as well as the benefit of using a protective wear cap to reduce adaptor wear, but obviates the need to machine the parts, eliminates creation of stress risers in either the wear cap or the adaptor, and additionally prevents the wear cap from inadvertently sliding off the adaptor during tooth replacement. As a result, the deficiencies of the previously employed protective wear caps have been eliminated without adversely affecting the attachment and securement means of the previously patented structure.